Document which factors are used to compute code owner scores

Users often ask about this, hence this information should be documented.
Also list factors that are not taken into account, but which are
frequently wanted, so that it's clear that these are currently not
supported.

Signed-off-by: Edwin Kempin <ekempin@google.com>
Change-Id: Idfdf191198dece8e0bf15ba064d9e4fcdc2118d9
diff --git a/resources/Documentation/rest-api.md b/resources/Documentation/rest-api.md
index fa7cb6b..e22d4b8 100644
--- a/resources/Documentation/rest-api.md
+++ b/resources/Documentation/rest-api.md
@@ -368,6 +368,16 @@
 assigned to '*') a random set of (visible) users is returned, as many as are
 needed to fill up the requested limit.
 
+The following factors are taken into account for computing the scores of the
+listed code owners:
+
+* distance of the code owner config file that defines the code owner to the
+  path for which code owners are listed (the lower the distance the better the
+  code owner)
+
+Other factors like OOO state, recent review activity or code authorship are not
+considered.
+
 #### Request
 
 ```